OCCUPANT DETECTION DEVICE AND OCCUPANT DETECTION METHOD

An occupant detection device (1) includes: an acquisition unit (101) configured to acquire, based on an intensity of a reflected wave generated when a transmission wave transmitted toward an interior of a moving body is reflected by an object present in the interior, point cloud information indicating a three-dimensional-coordinate position of the object moving in the interior as a point cloud including a plurality of detection points; a generation unit (102) configured to generate, based on the point cloud information, a seat row map for each seat row including a plurality of seating regions, the seat row map indicating a distribution of the detection points in a plane region corresponding to an arrangement direction of the plurality of seating regions and a height direction of the moving body; a setting unit (103) configured to set, on the seat row map, an upper end line along an upper end portion of a plane point cloud including two or more of the detection points; and an estimation unit (104) configured to estimate the number of occupants for each seat row based on a shape feature of the upper end line.